This invention relates to a linear motor and a stage system with the same, suitably usable in an apparatus such as a semiconductor exposure apparatus or a high precision processing machine wherein precise positioning is to be performed. The present invention also relates to an exposure apparatus and/or a device manufacturing method using such a linear motor or a stage system.
In an positioning system of nanometer order for use in a semiconductor exposure apparatus or a high precision processing machine, heat generation in a linear motor, which is a driving source, has an adverse influence on the positioning process. More specifically, the heat generation may cause thermal deformation of the structure of the machine and a temperature rise of air, which may result in a measurement error in a position measuring laser interferometer. It may also cause degradation of the positioning precision of the apparatus in which the linear motor is incorporated. For example, with a temperature rise of only 1xc2x0 C., a low thermal expansion material (thermal expansion coefficient 1xc3x9710xe2x88x926) of a size 100 mm may deform by 100 nm. Also, with a change of only 1xc2x0 C. or less in the temperature of air at the light path of an optical-interferometer distance gauge, an error of 100 nm may be produced in the measured value. In consideration of this, some measures should be taken to prevent such temperature change and, in this respect, a linear motor has to be cooled. Particularly, any heat produced from the linear motor should be collected.
On the other hand, in order to improve the performance of an apparatus, enlargement of the output power of a linear motor has been desired. If the electric current to be supplied to coils of the motor is made larger at this end, the amount of heat generation becomes larger. It requires enlargement of the cooling capacity. The enlargement of the cooling capacity is important also with respect to prevention of damage to the coil wires or an increase in coil resistance due to a coil temperature rise.
FIG. 15 is a sectional view of a structure of a conventional linear motor having cooling means. As illustrated, the linear motor comprises a coil 1 and permanent magnets 3 fixed to yokes 2 on the opposite sides of the coil 1. The coil 1 is surrounded by a jacket 9, which comprises thin sheets 4 and 4xe2x80x2 and a frame 5. The coil 1 is fixed to the frame 5 by means of a fixing element 7. The jacket 9 is structured so that a cooling medium flows through an inside space 6 thereof, to collect heat produced at the coil 1.
FIG. 16 is a sectional view of a linear motor of another example. In this linear motor, an electric current flows through a coil 1 (lateral in 5 the drawing) disposed in a magnetic field (longitudinal in the drawing) produced by permanent magnets 3, which are fixed to yokes 2. In response to it, the coil 1 and the magnets 3 are relatively moved in a direction perpendicular to the sheet of the drawing. In order to collect heat produced from the coil 1, the coil 1 is enclosed by a jacket having portions 14 and 14xe2x80x2. A cooling medium flows through a clearance between the coil 1 and the jacket, by which the heat is collected. In order that the distance between the permanent magnets 3 is made smaller and the produced magnetic density is made larger for enlargement of the linear motor thrust, the jacket is made thin.
In these examples, however, if the flow rate of the cooling medium is made larger to increase the cooling capacity, the resultant pressure rise of the cooling medium may cause outward deformation of a small-thickness portion of the jacket. It may result in contact with the permanent magnet or breakage of the jacket. To avoid this, the small-thickness portion of the jacket should have a sufficient strength. To the contrary, to increase the output power of a linear motor, the distance between permanent magnets has to be made small to enlarge the magnetic density. In this respect, the small-thickness portion of the jacket should be made thin as much as possible to reduce the size of the jacket.
Further, in a case of a multiple-phase linear motor having coils being arrayed along a direction perpendicular to the sheet of the drawing of FIG. 16, the coil and jacket structure extends in a direction perpendicular to the sheet of the drawing. In this example, the natural frequency of the structure should be made large to reduce the adverse influence on a high-precision positioning system in which the linear motor is incorporated.
It is accordingly an object of the present invention to provide a linear motor structure and/or a stage system with the same wherein the thickness of a small-thickness portion can be kept small while the strength of the same is enlarged.
It is another object of the present invention to provide an invention to provide a linear motor structure and/or a stage system with the same wherein a coil and jacket structure has an enlarged natural vibration frequency.
It is a further object of the present invention to provide an exposure apparatus and/or a device manufacturing system that uses a linear motor structure or a stage system such as described above.
In accordance with an aspect of the present invention, there is provided a linear motor, comprising: a magnet; a coil; and a jacket having an inside comb-shaped member extending along a driving direction, wherein the coil is engaged by teeth of the comb-shaped member and wherein a cooling medium flows through an inside space enclosed by the jacket.
The comb-shaped member may include base portions provided on mutually opposed inside faces of the jacket and formed in parallel to the driving direction and to be opposed to each other, and a pillar-like portion for connecting the base portions, wherein the coil may be supported by said base portions in a floating manner while it may be held fixed by the pillar-like portion with respect to the driving direction.
The linear motor may include a plurality of coils arrayed along the driving direction partially overlapping each other, wherein each coil may have a bent end portion to avoid mutual interference of the partially overlapped portions of the coils, and wherein the coils may be disposed with their central portions placed substantially at the same level.
The jacket may have a central portion of a small thickness with an outside recessed portion, wherein the bent end portions of the coils may be disposed at the recessed portion, and wherein the central portion of small thickness may be reinforced by the recessed portion.
The jacket may serve as a guide for an element to be driven by the linear motor.
In accordance with another aspect of the present invention, there is provided a stage system, comprising: a movable stage; a linear motor having a magnet and a coil, for driving the stage; and a jacket having an inside member that is comb-shaped, extending along a driving direction, wherein the coil is engaged by teeth of the comb-shaped member and wherein a cooling medium flows through an inside space enclosed by the jacket.
In accordance with a further aspect of the present invention, there is provided an exposure apparatus, comprising: a movable stage for holding a substrate thereon; a linear motor having a magnet and a coil, for driving the stage; and a jacket having an inside member that is comb-shaped, extending along a driving direction, wherein the coil is engaged by teeth of the comb-shaped member and wherein a cooling medium flows through an inside space enclosed by the jacket.
In accordance with a yet further aspect of the present invention, there is provided a device manufacturing method, comprising the steps of: applying a photosensitive material onto a substrate; exposing the substrate by use of an exposure apparatus including a movable stage for holding a substrate thereon, a linear motor having a magnet and a coil, for driving the stage, and a jacket having an inside member that is comb shaped, extending along a driving direction, wherein the coil is engaged by teeth of the comb-shaped member and wherein a cooling medium flows through an inside space enclosed by the jacket; and developing the exposed substrate.
In accordance with a still further aspect of the present invention, there is provided a linear motor, comprising: a magnet; a coil; and a jacket having a reinforcement portion extending parallel to a driving direction, wherein the coil is enclosed by the jacket and wherein a cooling medium flows through an inside space of the jacket.
The reinforcement portion may be formed on an outside face of the jacket.
The reinforcement portion may be formed at a position not interfering with relative motion of the magnet and the coil.
The reinforcement portion may be made of one of aluminum, ceramics and resin.
The reinforcement portion may be made integral with the jacket, and the reinforcement portion may be defined by a portion having a protruded shape with respect to a level of a portion of the jacket where the magnet and the coil are opposed to each other.
The jacket and reinforcement portion being integral with each other may be made of one of ceramics and resin.
The protruded shape portion of the jacket may be defined by an inside recessed portion of the jacket where a portion of the coil is placed.
At least one of an upper half and a lower half of a section of the jacket taken along a plane perpendicular to the driving direction may have a recessed shape portion.
In accordance with another aspect of the present invention, there is provided a stage system, comprising: a movable stage; a linear motor having a magnet and a coil, for driving the stage; and a jacket having a reinforcement portion extending parallel to a driving direction, wherein the coil is enclosed by the jacket and wherein a cooling medium flows through an inside space of the jacket.
In accordance with a further aspect of the present invention, there is provided an exposure apparatus, comprising: a movable stage for holding a substrate thereon; a linear motor having a magnet and a coil, for driving the stage; and a jacket having a reinforcement portion extending parallel to a driving direction, wherein the coil is enclosed by the jacket and wherein a cooling medium flows through an inside space of said jacket.
In accordance with a yet further aspect of the present invention, there is provided a device manufacturing method, comprising the steps of: applying a photosensitive material onto a substrate; exposing the substrate by use of an exposure apparatus having a movable stage for holding a substrate thereon, a linear motor having a magnet and a coil, for driving the stage, and a jacket having a reinforcement portion extending in parallel to a driving direction, wherein the coil is enclosed by the jacket and wherein a cooling medium flows through an inside space of the jacket; and developing the exposed substrate.
The comb-shaped member or the reinforcement member functions to enlarge the strength of the jacket against the pressure of the cooling medium inside the jacket. Thus, even if the pressure of the cooling medium is made larger or the size of the jacket is made smaller, unwanted deformation or breakage of the jacket can be prevented. A linear motor with its output power enlarged as compared with conventional structures can be provided, such that a stage system, an exposure apparatus or a device manufacturing method using such a linear motor can also be provided.
The comb-shaped member or the reinforcement member is provided in an inside space of the linear motor. Therefore, without the need of enlargement in size of the linear motor, deformation or breakage of the jacket can be prevented and, on the other hand, the cooling efficiency can be improved. Further, the provision of the comb-shaped member or the reinforcement member effectively improves the rigidity of the jacket, the natural frequency of the jacket can be made higher. This effectively leads to improvements in precision of a precision positioning apparatus or precision machining apparatus wherein the linear motor is incorporated.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.